Numerous types of fluids, blood, plasma, nutritive solutions and the like, are frequently injected into a patient undergoing medical treatment. The fluids are injected either under the force of gravity or under pressure supplied by a mechanical pump. The fluids which are to be injected are, of course, produced and stored in such a manner that they should be safe for direct injection into a patient. However, micro-organisms, particles or air may enter the fluid prior to its injection into a patient. Mechanical filtration of the fluids is intended to remove such micro-organisms, particles or air. However, prior art medical filtration devices have generally been expensive and, hence, are not always used during IV treatment.
Numerous types of filters have been used to filter medical treatment solutions. A number of prior art filter assemblies, such as exemplified in U.S. Pat. No. 2,765,923 to Novak, U.S. Pat. No. 3,949,744 to Clarke, U.S. Pat. No. 4,035,304 to Watanabe, and U.S. Pat. No. 4,066,556 to Vaillancourt, utilize flexible walls to contain the filter assemblies. The filtering mechanisms disclosed in the Watanabe and Vaillancourt patents have relatively complex structures wherein a filter media is folded within a bag-type housing. The filter assembly disclosed in the Novak patent includes a pair of flexible walls secured to a central filter media along the edges of the media. However, the central walls of the Novak filter assembly are not attached to the filter media and, hence, are free to move relative thereto.
A filter assembly which utilizes, a relatively rigid housing is illustrated in U.S. Pat. No. 4,021,353. Other types of filter assemblies that use rigid housings are produced by a number of manufacturers. Rigid walled filter assemblies generally have complex structures which result in high construction costs.